The terms "hominoid", "hominid", and "hominin" are not interchangeable,
but their classification criteria are variously in a state of flux. In
general, the hominoids are a primate superfamily; the hominid family is
currently considered to comprise both the great ape lineages and human
lineages within the hominoid superfamily; the "homininae" comprise both
the human lineages and the African ape lineages within the hominids, and
the "hominini" comprising only the human lineages. The current scheme
is as follows:

The term "hominins" almost always refers to the tribe Hominini, and not
to the subfamily Homininae. It is important to note that in the older
scheme (before about 1980), the Hominoids comprised the gibbons (Hylobatidae),
the great apes (Pongidae), and the Hominidae, with the Hominidae (hominids)
consisting only of the two genera Homo and Australopithecus. The new scheme
is therefore considerably different. For example, under the old scheme,
the statement "modern man is the only living hominid" is correct. Under
the new scheme, that statement is incorrect.

The human lineages (the hominins) are characterized by a number of features,
including bipedalism. In effect, hominins are the group of fossils more
closely related to modern humans than to any other group. In terms of
dating, the hominin group apparently originated sometime between 5 and
8 million years ago. Concerning the "apes", there are two categories of
relevance here: The term "great apes" refers to chimpanzees, gorillas,
and orangutans. The term "African apes" refers only to chimpanzees and
gorillas. The distinction is important, since on the basis of molecular
evidence, the African apes are close to humans, while the orangutans are
not that close, and the gibbons are even further removed.

The classification and interpretation of hominin fossils has never been
free of controversy, partly because hominin fossils are not that plentiful,
and perhaps partly because there are a number of rival discovery teams,
and the significance of a new hominin fossil discovery is enhanced if
the discovery apparently requires new classifications and/or new interpretations.